1. Field of the Invention
The present invention relates generally to data storage subsystems, and more particularly to methods of storing and retrieving data to and from tape backup systems and data storage subsystems.
2. Description of Related Art
U.S. patent application Ser. No. 09/274,789, filed Mar. 23, 1999, entitled ASYNCHRONOUS SHADOWING IN DATA STORAGE SUBSYSTEM, applicant, Christopher J. West and U.S. Patent Application filed concurrently herewith, entitled RETRIEVING DATA FROM A DATA STORAGE SUBSYSTEM, applicants, Christopher J. West and David G. Beal, are specifically incorporated herein by reference for all that they disclose and teach.
In today""s competitive business environment, a business must diligently protect its assets, including the data stored within its computer network. Safeguarding corporate data, including engineering designs, pricing information, corporate procedures, customer and vendor lists, and order information, is crucial to the long-term success of a business. Threats to corporate data include hardware failure, physical plant disasters (e.g., building fires, earthquakes, tornadoes, and hurricanes), theft, and industrial sabotage. Protecting corporate data through backup software helps alleviate the downside of these threats and therefore has become an essential part of managing computer network environments.
Data storage management methods in modem computer networks tend to vary according to different data characteristics and management issues, such as the amount of the data, cost, performance and fault tolerance. One particularly useful method of protecting business data is to periodically copy (or xe2x80x9cbackupxe2x80x9d) the data to an archive tape for storage at a remote location. Tape backup systems are typically employed for long-term type storage of data in case something happens to the local storage medium. The typical tape backup process copies all the data from the storage medium onto a series of tapes, usually referred to as a tape library.
Tape backup systems are connected to the local storage medium, such as a disk array, and to a local application host computer system which is used to control and manage tape backup procedures. Following a typical backup procedure, the tapes are shipped to a remote location as a precaution against physical catastrophe to the local building or structure which would most likely damage the disk array and the tape library. The tape backup process is conducted as often as necessary for the given application, but usually occurs once a day, and typically at night when the host computer is not accessing the primary storage controller since the backup process is relatively time consuming.
One particular drawback associated with tape backup systems is that the application host system cannot access the disk array during the tape backup procedure, i.e., during the xe2x80x9cbackup window.xe2x80x9d Even if the host system has some access to the disk array during the backup window, that access is usually quite limited and slows down the backup procedure significantly. Consequently, the host system is generally not used during the backup window creating a period of time wherein no operations are performed by the host application system. Moreover, backup procedures utilizing the tape system are typically performed as infrequently as possible in order to reduce the impact on the host system.
Another drawback associated with the normal tape backup procedure involves the retrieval of information from the tape library. Since the tapes are shipped to a remote location, the retrieval of data from a tape typically begins with the physical transportation of the tapes back to the local site. Once the tapes are received at the local site, the library must be attached to the system and the information must be located and downloaded back to the system. Locating and downloading data from the tape monopolizes the host application system and prevents other processes from being performed by the host system during the retrieval process. The inability to perform normal operations notably impacts host performance since data location and downloading procedures typically consume a significant amount of time.
Another disadvantage associated with typical tape backup systems relates to the fact that the tapes must be shipped from the primary site to the secondary, remote site. Such shipping involves additional time, effort and cost.
Alternative disaster-relief backup solutions involves substantially real-time archival of data. Such systems are generally referred to as xe2x80x9cremote copy systemsxe2x80x9d, wherein data is recorded fairly contemporaneously to a primary storage medium and a secondary storage medium located remotely from the primary site. The secondary storage medium, such as a disk array, is part of a remote, secondary storage system or subsystem that is connected to the primary storage system by a communications link. Data is transferred from the primary storage system to the secondary storage system using the communications link. The information on the secondary system is typically a relatively current copy of the data on the primary system.
Existing remote copy schemes include Peer to Peer Remote Copy (PPRC), which involves the synchronous propagation of information to the secondary system as changes occur, and Extended Remote Copy (XRC), which provides for asynchronous copying of information to the secondary system. The XRC approach copies portion of a primary volume, i.e., virtual disk, to the secondary system at predetermined intervals to provide improved access to the primary volume over the PPRC synchronous scheme. A third remote copy process involves the creation of a bridge or xe2x80x9csnap volumexe2x80x9d which is a copy of the primary volume. The snap volume is used to copy information to the secondary system which allows the host system to substantially fully access the primary volume at all times. This third process is referred to as data xe2x80x9cshadowingxe2x80x9d and is described in detail in the above referenced, co-pending patent application titled ASYNCHRONOUS SHADOWING IN A DATA STORAGE SUBSYSTEM.
Remote copy systems provide some notable benefits over the normal tape back up system. For example remote copy solutions provide the ability to create a substantially current backup of information at another site without the time consuming tape backup procedure. Moreover, the remote copy process involving the snap volumes occurs with minimal impact on the host system.
Unfortunately however, since the remote systems are designed primarily to provide disaster relief (such as when the local building is destroyed) these systems do not provide for the xe2x80x9cretrievalxe2x80x9d of information related to day-to-day type situations. Thus, to retrieve information from the remote system, selected information must be copied to a storage medium and physically transported to the local site, and downloaded to the local disk array. This process is similar to the tape system retrieval process with the added step of copying the information to the storage medium. As stated above, this type of retrieval is time consuming and significantly impacts the host application system.
Moreover, remote copy systems do not provide the longer-term type storage that tape systems provide. That is, since the secondary storage system has only one storage medium, i.e., disk array, at the remote site, the information on this disk array changes daily and almost as quickly as the information changes on the primary storage system. Longer term storage provides many benefits and consequently, many organizations employ both a remote copy system and a tape backup system while simply contending with the inadequacies of each.
It is with respect to these and other considerations that the present invention has been made.
The present invention provides a method and system providing a tape backup system at a remote location connected to a remote copy system to enhance the tape backup system functionality. An aspect of the present invention relates to a tape backup system wherein the backup copying of information to tape occurs remotely so tapes do not have to be shipped to a remote site. Another aspect of the present invention relates to a tape backup system wherein the tape backup procedure occurs while minimizing the impact on the host computer and its ability to access the local disk array. Yet another aspect of the present invention relates to a tape backup system incorporating taped data that is accessible to the host computer without physically shipping tapes to the host computer site.
In accordance with preferred aspects, the storage control system of the present invention has a primary storage system which has at least one local storage disk and a primary storage controller for controlling the allocation of data located on the local storage disk. The system also incorporates a remote storage system having at least one remote storage disk, and a secondary storage controller for controlling the allocation of data on the remote storage disk. The secondary controller is coupled to the primary storage controller to receive control signals from the primary storage controller. The secondary storage controller is also adapted to receive data transmissions from the primary storage controller and copy the data to the remote storage disk. The system also has a tape backup system located at the remote site and coupled to the secondary controller. The tape backup system is adapted to receive control signals from the secondary controller and data transmissions from the secondary controller. The tape backup system copies data located on the remote storage disk to the tape medium in response to backup control signals received from the secondary controller. The preferred system further comprises a remote host computer system coupled to the secondary controller and the tape backup system. The remote host computer system receives control signals from the secondary controller and responsively operates the tape backup system to copy data from the remote storage disk to the tape medium.
In accordance with other preferred aspects, the system asynchronously copies the data from the remote storage disk to the tape medium. Additionally, the secondary storage controller further comprises a snap volume to facilitate the asynchronous copying of the data from the remote storage disk to the tape medium.
In accordance with other aspects, the present invention relates to a storage control system for retrieving a remote copy of data from a tape medium wherein the system also comprises a primary storage system and a remote storage system. Again, the tape backup system having a tape medium is located at the remote site and coupled to the secondary controller. The tape backup system adapted to receive control signals from the secondary controller and to copy data from the tape medium to the remote storage disk in response to restore control signals from the secondary controller. Moreover, the secondary controller is adapted to transmit the information stored on the remote storage disk by the tape backup system to the primary storage controller to thereby create a local copy of the information on the remote tape backup system for use by the primary system.
In accordance with yet other preferred aspects, the present invention is adapted to store and retrieve selected portions of one or more volumes of information during a particular storing or restoring process. Additionally, the secondary storage controller is adapted to transfer the point-in-time copy located on the remote storage disk as indicated by a lookup table if such a valid copy exists in response to request for a point-in-time copy prior to searching the tape backup system.
The present invention also relates to methods of storing and retrieving data to a tape backup system to a primary storage system, wherein the tape backup system is remotely located from the primary system. The methods comprise the steps of coupling the tape backup system to a remote secondary storage system having at least one remote storage disk and a secondary storage controller and coupling the secondary storage controller to the primary storage system via a communications link. The storing method further comprises the steps of transmitting data from the primary storage system to the secondary storage system and transmitting data from the secondary storage system to the tape backup system, preferably asynchronously, using a snap volume.
The restoring method further comprises the steps of conducting a first restore control signal from the primary storage controller to the secondary storage controller and conducting a second restore control signal from the secondary storage controller to the tape backup system in response to the first restore control signal. Additionally, the method involves the copying of data located on the tape medium to the remote storage disk as controlled by the secondary storage controller in response to the second restore signal thereby creating a remote point-in-time copy on the remote storage disk and transferring the data associated with the remote point-in-time copy from the secondary storage controller to the primary storage controller thereby creating a local point-in-time copy. Preferably the secondary controller searches the remote disk array for a valid remote point-in-time copy prior to conducting the second restore control signal. If a valid remote point-in-time copy is found, the secondary controller transfers the point-in-time copy to the primary storage controller. If a valid remote point-in-time copy is not found, the secondary controller conducts the second control signal from the secondary controller to the remote host computer system.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.